Process for the production of porous phenolic resin fibers

Abstract

A process for the production of porous phenolic resin fibers is disclosed, which process comprises graft-polymerizing to phenolic resin fibers a vinyl group-containing monomer capable of forming a thermally decomposable polymer, and thereafter subjecting the fibers to a heat treatment at a temperature high enough to cause thermal decomposition of the graft polymer. The product thus obtained is excellent in heat-resistance and adiabatic property in addition to useful properties inherent to phenolic resin fibers.

What is claimed is: 
     
       1. A process for the production of porous phenolic resin fibers, comprising the steps of: providing phenolic resin fibers;   graft-polymerizing to the phenolic resin fibers a vinyl group-containing monomer to form a graft polymer linked to the phenolic resin fibers, and   heating the resulting phenolic resin fibers having the graft polymer linked thereto at a temperature of 150-300 ° C. to thermally decompose the graft polymer.   
     
     
       2. A process according to claim 1, wherein the vinyl group-containing monomer is capable of forming a homopolymer which is thermally decomposable at a temperature of 300 ° C. or less. 
     
     
       3. A process according to claim 2, wherein the vinyl group-containing monomer is a member selected from the group consisting of alkyl acrylates, alkyl methacrylates, vinyl halides, acrylonitrile and styrene. 
     
     
       4. A process according to claim 2, wherein the vinyl group-containing monomer is methyl methacrylate. 
     
     
       5. A process according to claim 1, wherein said graft-polymerization is performed so as to provide a grafting rate of 5-100%. 
     
     
       6. A process according to claim 1, wherein said graft-polymerization is performed so as to provide a grafting rate of 10-50%. 
     
     
       7. A process according to claim 1, wherein said heating step is performed at a temperature of 180-280 ° C. 
     
     
       8. A process according to claim 1, wherein said heating step is performed in the atmosphere of inert gas such as nitrogen or argon. 
     
     
       9. A process according to claim 1, further comprising treating the phenolic resin fibers having the graft polymer linked thereto with an organic extractant before said heating step to extract unreacted monomer and low molecular weight polymers which are not linked to the phenolic resin fibers. 
     
     
       10. A porous phenolic resin fibers obtained by a process according to claim 1.